The present invention relates generally to a new engine for use in, for example, personal watercraft. In particular, the present invention relates to a new four-stroke engine that was developed with a view to the future stricter environmental and emission regulations. The engine in accordance with the present invention has a flexible arrangement such that multiple engine components can be centrally located and interconnected. Furthermore, the engine can be easily adapted to accommodate a supercharger with minor adjustment.
There is a very popular type of watercraft known as a xe2x80x9cpersonal watercraftxe2x80x9d which is designed to be operated primarily by a single rider. Although this type of watercraft is commonly employed for single riders, frequently provisions are made for accommodating additional passengers although the maximum number of passengers is more limited than conventional types of watercraft.
This type of watercraft is also generally quite sporting in nature and normally accommodates at least the rider on a type of seat in which the rider sits in a straddle fashion. The passenger""s area is frequently open through the rear of the watercraft so as to facilitate entry and exit of the rider and passengers to the body of water in which the watercraft is operating, as this type of watercraft is normally ridden with passengers that are wearing swimming suits.
These personal watercraft are generally quite small so that they can be conveniently transported from the owner""s home to a body of water for its use. Because of the small size, the layout of the components is extremely critical, and this gives rise to several design considerations that are peculiar to this type of watercraft. However, due to its sporting nature it is also desirable if the watercraft is powered by an engine and propulsion device that are not only efficient but also generate sufficient power.
Traditionally, two-cycle engines have been used to power watercraft, including personal watercraft. These engines have the advantage that they are fairly powerful, relatively lightweight, and compact.
One particular disadvantage to the two-cycle engine is its emission content. Two-cycle engines generally exhaust larger quantities of hydrocarbons and other pollutants than four-cycle engines due to cylinder charging inefficiencies and the combustion of lubricating oil among other things. When measures are taken to reduce emissions of the two-cycle engine, other generally undesirable consequences can result, such as an increase in the weight of the engine, a reduction of its power output or the like. With concern for the environment and increasingly strict emissions requirements being instituted by various governing bodies. There is motivation to provide a power plant that reduces exhaust emissions while retaining other advantageous characteristics such as compactness, low weight and high power output.
Four-cycle engines are commonly used as power plants in other applications, such as automobiles. These engines have the advantage that their emissions output are generally desirably lower as compared to a two-cycle engine for a given power output.
It is an object of the present invention to provide a four stroke, three cylinder in-line engine having a compact construction.
It is another object of the present invention to provide a four stroke, three cylinder in-line engine having a modular construction to permit the interchange of parts between various engine models.
It is another object of the present invention to provide a four stroke, three cylinder in-line engine having improved exhaust emission characteristics.
It is another object of the present invention to provide a four stroke engine having a narrow and low profile.
It is another object of the present invention to provide a four stroke engine having a low profile valve actuation assembly for controlling the operation of the intake and exhaust valves.
It is another object of the present invention to provide a cylinder head having a low profile to reduce engine height.
It is another object of the present invention to offset the placement of the intake valves and exhaust valves with respect to a vertical axis within the cylinder head to reduce engine height.
It is another object of the present invention to provide an improved spark plug mounting assembly for easy access within the cylinder head.
It is another object of the present invention to provide a Y-shaped intake rocker arm assembly providing a compact construction.
It is yet another object of the present invention to provide a four stroke engine having an improved oil collection system and oil holding tank.
It is another object to provide a four stroke engine which combines a closed loop cooling system and an open loop cooling system for enhanced cooling of the engine in accordance with the present invention.
It is another object to provide an open loop cooling system for cooling an exhaust manifold in accordance with the present invention, wherein the open loop cooling system enhances cooling of the crankcase and cylinder head.
It is another object to provide an open loop cooling system for cooling an exhaust manifold in accordance with the present invention, wherein the open cooling system lowers the temperature of the exhaust manifold such that the exhaust manifold functions as a heat sink for the crankcase and cylinder head.
It is another object of the present invention to provide a closed loop cooling system for selectively cooling the crankcase and cylinder head of the four stroke engine.
It is another object of the present invention to provide a closed loop cooling system having a selectively operable heat exchanger.
The present invention is directed to a four stroke internal combustion engine having a flexible arrangement such that the engine can be easily configured for supercharged or normally aspirated operation.
The engine further includes a unique cooling system that includes both closed loop and open loop cooling systems for improved cooling efficiency.
The engine contemplated in accordance with the present invention includes a power take off housing located on one end of the crankcase. Various engine components are operatively coupled to the crankshaft within the power take off housing including a cam shaft for a valve actuation assembly, a generator, an engine starting mechanism, a balance shaft, and a supercharger.
The engine contemplated in accordance with the present invention also includes a unique dry sump lubrication system. The dry sump lubrication system includes a lubricant separator for separating lubricant from blow-by gas within the engine.